A non-human animal model is provided, particularly a mouse model for movement hyperactivity, excitoxicity disorders (e.g. myoclonic cramping) and neurodegeneration, in which modified cytoplasmic dynein heavy chain1 is expressed. Modified human and mouse cytoplasmic dynein heavy chain1 proteins and nucleic adds are also provided, including the corresponding recombinant proteins. The invention further provides uses for the non-human animal model and the modified cytoplasmic dynein heavy chain1 proteins and nucleic acids, in particular for the diagnosis and treatment of medical conditions associated with over-expression of cytoplasmic dynein heavy chain1.